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Regioselective Syntheses of 2,7-(Het)arylpyrido[2,3-d]pyrimidines by an Orthogonal Cross-Coupling Strategy. -Two sequential cross-coupling reactions of substrate (I) with arylboronic acids allow the approach to the desired target compounds. Monoarylated heterocycles (IIIa) and (IIIb) are most suitable in the process, whereas no reaction takes place in the presence of a pyridyl substituent [cf. (IIId)]. -(MAINGOT, L.; DEHBI, O.; BURON, F.; AADIL, M.; AKSSIRA, M.; ROUTIER, S.; GUILLAUMET*, G.; Synlett 2012, 17, 2449-2452, http://dx.

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An efficient and ecofriendly method for the synthesis of disubstituted 5-aminopyrimidines from vinyl azides and urea or thiourea was developed. This reaction proceeds under microwave irradiation conditions in the presence of water as a solvent. The remarkable features of this new protocol are high conversion, short reaction times, cleaner reaction profiles and straightforward procedure.

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Animal-bone-meal-supported palladium (0) was prepared and used as catalyst in the Suzuki coupling reaction in water, under sunlight as an alternative source of energy. This palladium has showed a high catalytic activity than tetrakis(triphenylphosphine) palladium (Pd(PPh 3) 4) in the Suzuki cross-coupling reaction (the reaction of 4-halogenopyridopyrimidine with boronic acids) in water via sunlight as the light source, with no addition of ligands. This green method affords heteroaryls with excellent yields in comparison with the classical method using tetrakis (triphenylphosphine) palladium. The green catalyst did not show any significant loss of activity, even when used up to five times.

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